N-(4-Methoxy-2-nitrophenyl)-2-(3-methyl-2-oxo-1,2-dihydroquinoxalin-1-yl)acetamide

The quinoxaline unit in the title molecule is slightly puckered [dihedral angle between the rings = 2.07 (12)°] while the whole molecule adopts an L-shaped conformation. The packing in the crystal is governed by C—H⋯O hydrogen bonds and slipped π-stacking interactions.

The quinoxaline unit in the title molecule, C 18 H 16 N 4 O 5 , is slightly puckered [dihedral angle between the rings = 2.07 (12) ] while the whole molecule adopts an L-shaped conformation. Intramolecular hydrogen bonding determines the orientation of the substituted phenyl ring and the amide nitrogen atom is almost planar. The packing in the crystal is governed by C-HÁ Á ÁO hydrogen bonds and slipped -stacking interactions.

Structure description
Quinoxaline and its derivatives have attracted significant considerations because of their pharmacological activities (e.g., Abad et al., 2021) and industrial properties (e.g., Laabaissi et al., 2020). As a continuation of our work on the synthesis of 3-methylquinoxalin-2-one derivatives in order to evaluate their pharmacological activities (Ramli et al. 2018), the title compound, C 18 H 16 N 4 O 5 was synthesized and its crystal structure is reported here.
The molecule adopts an L-shaped conformation with atom C10 at the apex of the 'L' (Fig. 1). The orientation of the pendant 2-nitro-4-methoxyphenyl ring is primarily determined by the strong intramolecular N3-H3AÁ Á ÁO1 and weaker C13-H13Á Á ÁO2 hydrogen bonds (Table 1). H3A may also participate in hydrogen bonding with O1, but this is a weak interaction at best due to the long H3AÁ Á ÁO1 separation (Table 1). The quinoxaline unit is not quite planar, as indicated by the dihedral angle of 2.07 (12) between the mean planes of the constituent rings. The dihedral angle between the mean planes of the C12-C17 and the C1/C6/N1/C7/C8/N2 rings is 81.96 (5) . The sum of the data reports interbond angles about N3 is 360 , which may be interpreted as the participation of its lone pair in bonding: this is supported by the N3-C11 and N3-C12 bond distances of 1.358 (2) and 1.408 (2) Å , respectively, which are shorter than would be expected for sp 2 (C)-sp 3 (N) bonds.

Figure 1
The title molecule showing 50% displacement ellipsoids. The intramolecular hydrogen bonds are depicted by dashed lines.
reflux at 80 C. When the starting reagents had completely reacted, 500 ml of distilled water were added and a few minutes later the product precipitated. This was filtered, dried and recrystallized from hot ethanol solution to yield lightyellow plate-like crystals of the title compound.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

data-1
IUCrData (  Special details Experimental. The diffraction data were obtained from 10 sets of frames, each of width 0.5° in ω or φ, collected with scan parameters determined by the "strategy" routine in APEX4. The scan time was θ-dependent and ranged from 10 to 30 sec/frame. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. H-atoms attached to carbon were placed in calculated positions (C-H = 0.95 -0.99 Å) and were included as riding contributions with isotropic displacement parameters 1.2 -1.5 times those of the attached atoms. That attached to nitrogen was placed in a location derived from a difference map and refined independently.